1. Field of the Invention
The present invention relates to a scroll-type compressor assembly for compressing a working fluid and lubricated with an oil, for use in an air conditioning system, and particularly to a scroll compressor assembly for use in an automotive air conditioning system, and to features for distributing oil within scroll compressor assemblies and using the oil for hydrodynamically separating and supporting relatively moving surfaces therein.
2. Description of the Related Art
Scroll-type compressor assemblies for automotive air conditioning systems are well-known in the art. A compressible working fluid such as a refrigerant gas is received into the compressor assembly housing at a suction pressure and discharged therefrom at a relatively higher discharge pressure. In automotive air conditioning systems, a scroll compressor assembly typically has a drive shaft whose rotation axis is generally horizontal and driven by the engine crankshaft through a drive belt coupled to the engine crankshaft pulley, which serves as a rotative power source. The compressor drive shaft is coupled to a compression mechanism within the compressor housing, which may be defined by front and rear casings. The compression mechanism of a scroll compressor assembly typically has an orbital scroll member coupled to the drive shaft and a nonorbital scroll member with which it is operably engaged. The orbital scroll member is driven in a generally circular orbit about the drive shaft rotation axis relative to the nonorbital scroll member.
The orbital scroll member includes a plate with a flat, inner surface that is perpendicular to the rotation axis and an involute wrap integral with the plate and extending out from the inner surface. The cooperating nonorbital scroll member includes a plate with a flat, inner surface that interfaces and is parallel to the inner surface of the orbital scroll member, and an involute wrap integral with its plate that extends from its inner surface. The wraps and flat, inner surfaces of the orbital and nonorbital scroll members cooperate to form fluid pockets which are bound by adjacent surfaces of the interengaged scroll members. These boundaries are established by line contacts between the intermeshed wraps, and contact between the axial tips of the intermeshed wraps and the inner surfaces of the scroll member plates against which the wrap tips are slidably engaged. A seal is normally provided in a groove formed in the axial tip of each involute scroll wrap, to seal between the wrap and the inner surface of the adjacent scroll member plate against which it slides. The axial tip seals are provided to accommodate thermal expansion of the scroll members, and separation therebetween that may result from the forces induced by the compressed fluid in the fluid pockets. An example of a prior such scroll compressor assembly is described in U.S. Pat. No. 5,346,376 (Bookbinder et al.) issued Sep. 13, 1994, the disclosure of which is expressly incorporated herein by reference.
The working fluid at substantially suction pressure, and in which substantially incompressible lubricating oil is entrained, is received in a compression mechanism inlet between the scroll members at a radially outward location. The working fluid/oil admixture received by the compression mechanism is captured within the fluid pockets defined by the interengaged scroll wraps as the orbital scroll member moves about the shaft rotation axis relative to the nonorbital scroll member. The entrained oil lubricates and cools the interengaged scroll members.
During compressor operation, as the orbital scroll member is driven by the rotating shaft, the contact lines and the fluid pockets defined between the intermeshed wraps move along the surfaces of the wraps toward the centers of the cooperating scroll members. The fluid pockets become smaller in volume as they move along the wraps toward the centers of the scroll members, and the working fluid in the fluid pockets is compressed. Thus, the interengaged orbital and nonorbital scroll members define the compression mechanism, and the fluid pockets define compression chambers of the compression mechanism in which the pressure of the contained working fluid/oil admixture is raised from substantially suction pressure to a relatively higher, substantially discharge pressure. A fluid discharge aperture is provided near the center of the nonorbital scroll member, providing a passageway through which the compressed admixture is expelled from the compression mechanism at substantially discharge pressure.
The orbital scroll member plate has an outer face that is located on the outside of the compression mechanism and opposite its flat, inner surface. Defined on the outer face is a flat thrust surface that is substantially parallel with the inner surface. Opposing the axial forces induced by the compressed admixture within the compression mechanism is a planar thrust washer disposed between the thrust surface of the orbital scroll member and a superposed, flat, rear-facing surface of the front casing of the housing. The thrust washer may be retained against movement relative to the front casing, and may include apertures that, with the rear-facing front casing surface, define pockets in which oil is disposed; the oil in these oil pockets lubricates the sliding interface between the thrust washer and the orbital scroll member thrust surface. Such a thrust washer/thrust surface interface is disclosed in above-mentioned U.S. Pat. No. 5,376,376. Despite the presence of such oil pockets, the compressor assembly may still experience frictional losses due to the sliding engagement of the orbital scroll member thrust surface and the thrust washer, particularly if oil is not adequately replenished to the oil pockets.
Conventional thrust bearing assemblies employing needle roller bearings or ball bearings may be positioned between the thrust surface, and the thrust washer or the rear-facing surface of the front casing to axially support the orbital scroll member relative to the housing. Often, such thrust bearing assemblies, though intended to reduce frictional losses, either do not adequately accommodate the orbital motion of the thrust surface relative to the thrust washer or front casing surface, or add significantly to the complexity and/or cost of the compressor assembly. Furthermore, such thrust bearing assemblies have moving parts, the introduction of which may contribute to potential durability concerns in a compressor assembly, particularly if the thrust bearing assemblies are inadequately lubricated.
It would be beneficial if, during compressor operation, lubricating oil were continually distributed to the interface between the orbital scroll member thrust surface and the thrust washer, and was also used for hydrodynamically separating and supporting the orbital scroll member thrust surface relative to the thrust washer and the front casing. Such an improvement would reduce frictional losses without introducing additional complexity or cost, or the potential durability concerns often associated with incorporating additional moving parts.